The proposed revision to R01HD074346 is designed to extend the project to a new disorder: autism spectrum disorder (ASD). Promising new pharmacological and behavioral treatments are being developed for numerous intellectual and developmental disabilities (IDD), including ASD. Evaluation of these treatments, however, is hampered by a lack of adequate outcome measures. Beginning 03-01-2013, our team was funded to evaluate the adequacy of expressive language sampling (ELS) for deriving outcome measures. In ELS procedures, samples of spoken language are collected in highly structured, yet naturalistic, interactions. The samples are analyzed to derive outcome measures reflecting important dimensions of language skill and atypical language behavior. ELS procedures yield clinically relevant and functional endpoints, capture language impairments common to IDD as well as impairments specific to particular IDDs, and yield robust indicators of developmental change within typical and language-impaired populations. In the already funded project, we are focused on children, adolescents, and young adults with fragile X syndrome (FXS) and Down syndrome (DS). In terms of specific aims, we are (1) examining the basic psychometric properties of measures derived from ELS procedures, including test-retest reliability, internal consistency, validity, and sensitivity; (2) evaluating differences in the psychometric properties o ELS procedures as a function of variations in participant etiology, age, gender, autism symptom severity, and IQ; (3) comparing the psychometric properties of three different ELS contexts (conversation, narration, and the Autism Diagnostic Observation Schedule-2); and (4) evaluating the feasibility of implementing ELS procedures across multiple sites. Test-retest reliability is being assessed at 4 weeks (+/- 1 week) using alternate versions of ELS materials. Internal consistency is being assessed by computing alpha coefficients within and across sampling contexts. Norm-referenced standardized tests and informant report are the indicators of construct validity. Longitudinal follow-up will yield an estimate of sensitivity to change relatve to existing measures. In this revision, we propose to add participants with ASD, which is a population that overlaps with FXS and DS (e.g., many individuals with ASD have a comorbid intellectual disability). At the same time, however, ASD is associated with a wider range of language and cognitive abilities than is FXS or DS, which has made the task of identifying valid outcome measures more challenging. ASD participants will be tested at two new sites (University of Minnesota and University of Washington), as well as at UC Davis. The data collected will be relevant to all four specific aims of the already funded project, but offers a fuler evaluation of the generalizability of ELS procedures and adds ASD, a highly prevalent IDD condition in desperate need of new tools for evaluating treatment efficacy.